Ultra high frequency generator



Dec. 12, 1944. LUDl ULTRA HIGH FREQUENCY GENERATOR Original Filed March 6, 1941 MWWMIWWWW order to produce 'tions a velocity variation in accordance with an homogenous velocity.

Patented Dec lZ, 1944 2,364,113; ULTRA man FREQUENCY GENERATOR Fritz Liidi, Baden, Switzerland, assignor to Pat elhold Patentverwertungs- 8a Elektro-Holding A.-G., Glarus, Switzerl P ny and, a joint stock com- Original application March 6, 1941, Serial No. 382,089, now Patent No. 2,323,613, dated July 6, 1943. Divided and this application October 8,

/1'942, Serial No. 461,32

man-y 28. 1940 12 Claims.

With ultra short wave generators operating according to the principle of phase focussin g, in ultra high frequency oscilla-' ultra high frequency .period is impressed in a modulator on an electron beam having an initial locity variation more or less definite groups of electrons are formed at a certain distance be- ,yond the modulator, these electrons producing alternating voltages of ultra high frequency in a 1. In Switzerland Feb- (Cl. sis- As a result of this veso-called inductor. The self-excitation of such a generator is brought about by means of a feedback arrangement whereby the voltages occur ing in the inductor are fed back to the moduator.

' A particularly favourable feed-back arrangement is known, which only requires a single resonator which is connected to the inductor and modulator in-such a manner that the amplitude of the ultra high frequency voltages is smaller at the modulator-than at the inductorgan ultra high frequency load being coupled to the resonator providing the feed-back.

The present invention concerns an ultra short wave generator, in which the resonator which acts as the feed-back between the inductor and the modulator consists of a tubular wave conductor. one end of which at least is closed electrically, the inductor and modulator being arranged in such a manner inside the hollow space of the conductor and being provided with antennae so that the coupling between them is brought about by the-ultra high frequency waves occurring in the hollow space inside the conductor. Compared with ar rangements using Lecher systems and concentric tubular conductors, a wave conductor which is closed electrically at one end ofiers considerable advantages when employed for tubes with phase fooussing. The oscillations thus produced can then be passed ductor or be radiated into space. The assembly of a phase-focussing generator employing a wave conductor as a resonator is very simpleand possesses the advantage that all highly stressed elec-, trodes can be cooled directly. Furthermore with very short waves it is especially favourable when the natural frequency of such a resonator is mainly determined by the bore of the conductor tube and not by the axial length as is the case, with a Lecher system or a concentric pipe, whilst the axial length can be made as long as is desired. I r

This modified form 'of the invention is illusstructional examples shown in Figs. 1 to 10 of the accompanying drawing.

In the drawing, Fig. l is a longitudinal section through agenerator embodying the tion;

Fig. 2 is a partial representation in section of a fitting to connect the generator witha load;

Fig. 3 is a sectional representation of a fitting for the radiation of erator;

Fig. 4 isa transverse section on line 4-4 of Fig. l; i

Fig. 5 is a diagrammatic representation of the electrical field distribution obtained with the inductor antennae of Fig. 4;

directly through the wave conr Fig. 6 isa transverse section on line 6 -5 of a transverse section, and Fig. 8 is a longitudinal section, showing a modification of the arrangement of the inductor antennae;

Fig. 9 is a diagrammatic representation of the electrical field distribution obtained with the inductor antennae of Figs. 7 and 8, and

Fig. 10 is a transverse sectionshowing the preferred arrangement of the anode supports used Fig. '7 is in connection with the inductor antennae of Figs.

7 and 8.

According to the longitudinal section shown in- Flg. 1 the resonator forming the feed-back between the inductor 8 and the modulator 5 conthe coupling between the modulator and inductor is achieved by means of the ultra high frequency waves generated in the hollow space of the wave conductor. These antennae are fixed inside the wave conducting tube and serve at the same time as supports for the inductor and modulator electrodes. Inductor B; modulator 5 and anode H are not located in an insulator housing invacuum space of the generator, but to avoid un desirable reflections at such insulator elements are supported freely inside the wave conductor as shown in Figs. 4 and 6 which depict cross-sections on the lines 4-4 and B6 respectively in Fig. 1. The entire hollow space inside the con- "ductor 32, at least between the modulator, inductrated diagrammatically by means of the contor and anode thus also belongs to the vacuum space of the. generator. At the modulator end the conductor tube 32 is terminated by a metal principles of the invenoscillations from the gencover plate l which possesses a central aperture through which the electron beam enters. If desired a coarse mesh grid electrode can be located in this aperture. This aperture is covered by a tube head-piece ill of insulating material in which the filament I, cathodeZ, Wehnelt cylinder 3 and any other additional electrodes for forming and'accelerating the electron beam, together with the current leads, are located. The cylindrical extension of the cover plate i shown in the drawing can serve as an accelerating electrode if the positive pole of a high voltage direct current supply is connected to the metallic conductor tube.

To enable the wave conductor tube 32 to be coupled to an ultra high freqeuncy load it is provided with an extension beyondthe anode l i. If the oscillations are to be radiated directly into space the wave conductor tube 32 can be provided with a funnel-shaped end piece 33 as shown in Fig. 3, this. end piece being so dimensioned that the wave resistance of the freespace is' adjusted in the best possible manner to suit the generator. If, on the other hand, the ultra high frequency load is located some distance .awayfrom the generatorand if the high frequency energy produced is to be used in the form of electric alternating-currents which circulate in wire conductors, it is expedient to equip the extension 32' of the conductortube with a metallic cover plate 3Q asi indicated in Fig. 2 and an antenna 35, which for coupling the load circuit extends into the tube 32 and supplies a power conductor, for instance a concentric tubular conductor 30,- 3l, which is connected to'the load. With the constructional form illustrated erable to shut ofi the vacuum space of the genin Fig. 2 care must be taken that the distance of the cover plate 3.4 from the cover plate 4 at the modulator end of the tube is an even multiple of twice the distance between the inductor B and the cover plate 3d, so that in wave conductors which are thus closed at both ends standing waves are excited and the inductor is located at the point where the electrical fields are a maximum. Under these conditions the modulator 5 will thus receive ultra high frequency voltages whose amplitude corresponding to their distance from the cover plate l is smaller'than the amplitudes prevailing at the inductor electrodes. If, however, the wave conductor 32 shown in Fig. 1 is equipped with a funnel- 33.. (Fig. 3) then, on

condition that the funnel is correctly adjusted;

there will only be a standing wave between thecover plate l and the inductor 8, whilst beyond the inductor B there will only be a progressing wave which is. radiated by the funnel without reflection.

The funnel-shaped end piece shown in Fig- 3 or the cover plate in Fig. 2, both of which must have the same diameter at the lower flange ends of extension 32' as the wave, conductor tube 32 in Fig. 1, can be connected galvanicallyand vacuum-tight t the tube ea. In order to limit the" vacuum space an insulating piece must then, howductor.

inductor antenna.

erator to be universally used it is, however, pref 7s erator as shown in Fig. 1 by means of a special wall 36 of insulating material which should expediently consist of ceramic material with small dielectric losses, Whilst on the other side of this wall the tube conductor is provided with an extension into the atmosphere as indicated by the member 32'. The extension 32 can then also be fitted with a funnel as shown in'Fig. 3 or an electrical cover plate as indicated in Fig. 2. The dis-.

tance between the insulating wall 36 and the cover plate 4 isthen also selected to be equal to a whole number multiple of twice the distance between the inductor and the cover plate d, so that the reflected waves due to the electrical losses in the insulating wall 36 are in phase with the standing waves between the inductor and cover plate t.

By employing a wave conductor which is at least shut ofi at one end as afresonator for determining the frequency, very considerable advantages can be obtained as regards ultra short waves for generators operating with phase focussing. The natural frequency is namely mainly fixed by the size of the tube section and the form of excitation so that the tube length can be selected as desired. The distance between the cover plate 3 and the inductor 8 can thus be a multiple of the wave length generated in the free space, so that the geometric dimensions of the generator never become abnormally small even for the shortest waves in the centimetre range, such as would be the case if a Lecher system or concentric-tubular conductors were used. Al

though the electron beam is moves forward through the hollow' spacein the wave conductor it is possible by means of a special excitation to prevent any axial velocity variation of the electron beam in the direction of its expansion which might be caused by the electric field in the wave conductor. This is achieved by exciting the wave conductor in so-called H-waves which only pos-- sess a magnetic but not anelectrical alternating field in the axial direction. For the excitation of H-waves the antenna M, I5 connected to the inductor electrodes 9,10 must be located in the same plane perpendicular to the axis of the wave con- With the inductor antenna arranged as shown in Fig. 1 of which a cross-section is shown in Fig. 4, so-called Hl-WSNES are formed whose path in the-tube 32 is indicated in Fig. 5. The arrows in Fig. 5 reverse their direction after each half period of the alternating field. A comparison of Figs. 4 and 5 shows that the electrical field is mainly perpendicular to the direction of the To prevent the leads 3! to the anode H in Fig. 6 from disturbing the electrical field, these must be located perpendicular to the latter. For the Hi-waves the anode H including the leads 37, which at the same time serve to fix the former, must be arranged as shown in Fig; 6. With'H1-waves it is also unfavourable that the electrical field (Fig. 5) is strongest in the vicinity of the axis of the wave an annular cross-section it high frequency waves within said tube.

. For this purp se the inductor electrodes 9 and I voltages are produced are providedwith antennae M and I which are located at 90 to each other as shown in'Flg's. 7 and 8, it being'of no importance if the inductor electrode 9 is only connected to the antenna IE or to both antennae l5 and G5. On condition that the antennae for both inductor electrodes have the same form, for instance double antennae for each electrode as shown in the figure, an electrical field distribution as indicated in Fig. 9 will be obtained, so that thereare practically no electrical lines of force at the axis and therefore no disturbing influence on the electron beam. In accordance with the field distribution shown in Fig. 9 the anode supports 31 are located as indicated in Fig. 10 so that the anode I I and the supports 31 do not disturb the electrical field; Excitations of a higher order than the second are very rarely an advantage and only then when it is a question of generating extremely short waves. An excitation of the second order as described above is adequate in every respect for obtaining a space at the axis which is not subject to an electrical field. Instead of wave conductors with is also possible for instance to employ conductors with a rectangular cross-section, without in any way affecting the fundamental properties of the generator. It is preferable if the modulator antennae are of the same construction as the inductor antennae and are arranged parallel to the latter. The antennae of the inductor and modulator and also the anode supports 3'! (Figs. 6 and 10) can also serve as supply and discharge conduits for a liquid cooling medium which is used to car y'aw y t power losses at the inductor and modulator electrodes and also at the anode. In order to cool these parts it is often sufiicient if only the wave conductor tube 32 in Fig. 1 is cooled by a liq id cooling medium.

This application is a division of my application Serial No. 382,089, filed March 6, 1941 now U. S. Patent No. 2,323,613.

I claim:

1. An ultra short wave generator comprising means for generating an electron beam in an evacuated space, a modulator comprising a pair of gridelectrodes positioned in the path of said beam for subjecting the beam to ultra high frequency potential variations whereby ultra high frequency velocity variations are produced in the beam, an inductor comprising a pair of grid electrodes positioned in the path of the modulated beam whereby ultra high frequency alternating voltages are produced in said inductor, and a feed-back connection between said modulator and said inductor comprising a single resonator to which the ultra high frequency load is to be connected, said resonator comprising a-wave conductor tube which is electrically closed at one end, the inductor and the modulator bein positioned within said tube and provided with antennae whereby the coupling between the inductor and the modulator is effected by the ultra 2. An ultra short wave generator comprising means for generating an electron beam in an evacuated space, a modulator comprising a pair of grid electrodes beam for subjecting the beam to ultra high irequency potential variations whereby ultra high frequency velocity variations are produced in the beam, an inductor comprising a pair of grid electrodes positioned in the path of the modulated beam whereby'ultra high frequency alternating positioned in'the path of said.

in said inductor, and a feed-back connection between said modulator and said inductorcomprising a singl resonator to which the ultra high frequency load is to be connected, said resonator comprising a wave conductor tube which is electrically closed at one end. the inductor. and the modulator being positioned within said tube and provided with antennae whereby the coupling between the inductor and the modulator is efiected by the ultra high frequency waves within said tube, said antennae also supporting the inductor and the modulator fromsald tube.

3. An ultra short wave generatorcomprising means for generating anelectron beam in an evacuated space, a modulator comprising a pair of grid electrodes positioned in the path of said beam for subjecting the beam to ultra high fre- ,quency potential variations whereby ultra high frequency velocity variations are produced in the beam, an inductor comprising a pair of grid electrodes positioned in the path of the modulated beam whereby ultra high frequenc alternating voltages are'produced in said inductor, and a feed-back connection between said modulater and said inductor comprising a single resonator to which the ultra high frequency load is to be connected, said resonator comprising a wave conductor tube which is electrically closed at one end, theinductor and the modulator being positioned within said tube and provided with antennae whereby the coupling between the inductor and the modulator is effected by the ultra high frequency waves within said tube, the wave conductor tube at the modulator end thereof being provided with a metallic cover plate having a central aperture and a head piece of insulating material carrying the current leads to the electron beam generating means.

a. An ultra short wave generator as defined in claim 3 in which the wave conductor tube is closed at the end opposite from the modulator at a distance from said metallic cover plate which is a whole number multiple of twice the distance between the modulator and said cover plate.

5. An ultra short wave generator as defined in claim 3 in which the wave conductor tube is closed by an insulating cover plate at the end opposite from the modulator at a distance from said metallic cover plate which is a whole number multiple of twice the distance between the modulator and said cover plate and an extension of said tube beyond said insulating cover plate.

6.'An ultra short wave generator as defined in claim 3 in which the wave conductor tube is closed by arr insulating cover plate at the and opposite from the modulator at a distance from said metallic cover plate which is a whole number multiple of twice the distance between the modulator and said cover plate and an extension said metallic cover plate which is a whole number multiple of twice the distance between the modulator and said cover plate and an exten-. sion of said tube beyond said insulating cover plate including a. metallic cover plate for the extension and an antenna projecting into the extension and connected to a conductor leading to the ultra high frequency load.

8. An ultra short wave generator comprising means for generating an electron beam in an evacuated space, a modulator comprising a pain end, the inductor and the modulator being positioned within said tube and provided with antennae whereby the coupling between the inductor and the modulator is effected by the ultra high frequency waves within said tube, the antennae connected to the inductor being located in a plane perpendicular to the axis of the tube whereby H-waves possessing magnetic but no electrical components in the axial direction of the tube are excited.

9. An ultra short wave generator comprising means for generating an electron beamin an evacuated space, a modulator comprising a pair of grid electrodes positioned in the path of said beam for subjecting the beam to ultra high frequency potential variations whereby I ultra high frequency velocity variations are produced in the beam, an inductor comprisin apair of grid electrodes positioned in the path of the modulated beam whereby ultra high frequency alternating voltages are produced in said inductor, and a feed-back connection between said modulator and said inductor comprising a single resonator to which the ultra high frequency load is to be connected, said resonator comprising a wave conductor tube which is electrically closed at one end,"the inductor and the modulator being positioned within said tube and provided with antennae whereby the coupling between the inductor and the modulator is eifected by the ultra high frequency wav'es within said tube, the antennae connected to the inductor 'being located in a plane perpendicular to the axis of the tube and positioned angularly with respect to each other whereby H-wave's of an order higher than 1 having only weak electrical forces in beam, an inductor comprising a pair of grid electrodes positioned in the path of the modulated beam whereby ultra high frequency alternating voltages are produced in said inductor, and a feed-back connection between said modulator and said inductor comprising a single resonator to which the ultra high frequency load is to be connected, said resonator comprising a wave conductor tube which is electrically closed at one end, the inductor and the modulator being positioned within said tube and-provided with antennae whereby the coupling between the inductor and the modulator is effected by the ultra high frequency waves within said tube, the antennae connected to the inductor being located in a plane perpendicular to the axis of the tube and positioned at 90 with respect to each other whereby Hz-waves having only weak electrical forces in the vicinity of the tube axis are excited.

11. An ultra short wave generator as defined in claim 8 wherein the anode is attached to the v, wave conductor tube by means of supporting members positioned in a plane perpendicular to the tube axis and at right angles to the electric lines of force ofthe H-Waves.

12. An ultra short wave generator as defined r in claim 8 wherein the antennae connected to the modulator are parallel to the antennae connected to the inductor.

FRITZ LU'DI. 

